812
FXUS21 KWNC 072013
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST FEBRUARY 07 2024
SYNOPSIS: FOLLOWING A RESPITE FROM THE STORMINESS ADVERSELY AFFECTING THE
WESTERN CONTIGUOUS U.S. (CONUS) THIS WEEK, STRONG MID-LEVEL LOW PRESSURE IS
EXPECTED TO RETURN, LEADING TO AN ELEVATED RISK OF HEAVY PRECIPITATION, HIGH
ELEVATION HEAVY SNOWFALL, AND HIGH WINDS ACROSS MANY PARTS OF WEST COAST AND
INTERIOR WEST DURING WEEK-2. SHORTWAVE ENERGY FAVORED DOWNSTREAM IS EXPECTED TO
PROMOTE INCREASED CHANCES FOR HEAVY PRECIPITATION ACROSS THE SOUTH-CENTRAL AND
SOUTHEASTERN CONUS. AN EXPANDING AREA OF MID-LEVEL HIGH PRESSURE OVER ALASKA IS
EXPECTED TO LEAD TO UNSEASONABLE WARM AND DRIER THAN NORMAL CONDITIONS
THROUGHOUT MUCH OF THE STATE.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR CALIFORNIA, AND PARTS OF THE PACIFIC
NORTHWEST, NEVADA, AND THE DESERT SOUTHWEST, FRI-WED, FEB 16-21.
MODERATE RISK OF HEAVY PRECIPITATION FOR CALIFORNIA, FAR SOUTHERN NEVADA, AND
PARTS OF ARIZONA, SAT-WED, FEB 17-21.
SLIGHT RISK OF HEAVY SNOW FOR THE HIGHER ELEVATIONS OF CALIFORNIA, AND PARTS OF
OREGON, FRI-WED, FEB 16-21.
SLIGHT RISK OF HEAVY SNOW FOR PARTS OF THE HIGHER ELEVATIONS OF THE SOUTHERN
GREAT BASIN AND FOUR CORNERS, SAT-WED, FEB 17-21.
MODERATE RISK OF HIGH ELEVATION HEAVY SNOW FOR PARTS OF THE SIERRA NEVADA'S OF
CALIFORNIA, SAT-WED, FEB 17-21.
MODERATE RISK OF HIGH ELEVATION HEAVY SNOW FOR THE MOGOLLON RIM OF THE DESERT
SOUTHWEST, SAT-TUE, FEB 17-20.
SLIGHT RISK OF HIGH WINDS OVER MUCH OF THE WEST COAST AND PARTS OF THE INTERIOR
WEST, FRI-WED, FEB 16-21.
SLIGHT RISK OF HEAVY PRECIPITATION OVER THE SOUTHERN PLAINS, AND LOWER
MISSISSIPPI VALLEY, THU-SAT, FEB 15-17.
SLIGHT RISK OF HEAVY PRECIPITATION OVER PARTS OF THE LOWER MISSISSIPPI AND
TENNESSEE VALLEYS, SOUTHERN APPALACHIANS, SOUTHEAST, AND LOWER MID-ATLANTIC,
SAT-TUE, FEB 17-20.
SLIGHT RISK OF HIGH WINDS OVER THE GREAT LAKES, OHIO VALLEY, APPALACHIANS,
MID-ATLANTIC, AND NORTHEAST, THU-MON, FEB 15-19.
DETAILED SUMMARY
FOR SATURDAY FEBRUARY 10 - WEDNESDAY FEBRUARY 14:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY FEBRUARY 15 - WEDNESDAY FEBRUARY 21: TOWARDS THE MIDDLE OF NEXT
WEEK, DYNAMICAL MODELS CONTINUE TO BE IN GOOD AGREEMENT WITH THE 500-HPA HEIGHT
PATTERN OVER WESTERN NORTH AMERICA, FEATURING LONG-WAVE TROUGHING OVER THE
EASTERN PACIFIC, AND AMPLIFIED RIDGING CENTERED OVER NORTHWESTERN CANADA. OVER
TIME, MUCH OF THE ANOMALOUS TROUGHING IS EXPECTED TO SHIFT EASTWARD, CONSISTENT
WITH THE RETURN OF ENHANCED ONSHORE FLOW AND HEAVY PRECIPITATION POTENTIALLY
AFFECTING THE WESTERN CONUS DURING THE PERIOD. ALTHOUGH BOTH THE GEFS AND ECMWF
BASED INTEGRATED VAPOR TRANSPORT (IVT) REMAIN MOSTLY MODEST WITH ATMOSPHERIC
RIVER (AR) POTENTIAL, THERE IS AN UPTICK IN IVT SIGNALS DURING THE MIDDLE AND
LATTER PORTIONS OF WEEK-2 RELATIVE TO YESTERDAY, WHICH ALIGNS WELL WITH THE
TIMING OF THE SOUTHWESTERLY MID-LEVEL FLOW MOVING ONSHORE IN THE ENSEMBLES. IN
ADDITION, RAW ENSEMBLE PRECIPITATION TOOLS FAVOR WETTER CONDITIONS, WITH A
NOTABLE INCREASE IN PRECIPITATION OVER PARTS OF NORTHERN AND CENTRAL CALIFORNIA
RELATIVE TO PREVIOUS GUIDANCE.
GIVEN CONTINUED SUPPORT IN THE PROBABILISTIC EXTREMES TOOLS (PETS) WHICH SHOW
INCREASED CHANCES FOR 3-DAY PRECIPITATION AMOUNTS EXCEEDING THE 85TH PERCENTILE
AND 1 INCH, A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS ISSUED WITH ITS
COVERAGE NOW EXTENDING NORTHWARD INTO PARTS OF THE PACIFIC NORTHWEST AND
WESTWARD INTO THE LOWER FOUR CORNERS FOR FEB 16-21. EMBEDDED WITHIN THE SLIGHT
RISK AREA, A MODERATE RISK OF HEAVY PRECIPITATION REMAINS POSTED (FEB 17-21)
AND IS LIKEWISE EXPANDED WHERE PETS INDICATE HIGHER CHANCES (30-40%) FOR
AMOUNTS EXCEEDING THE 85TH PERCENTILE AND AMOUNTS APPROACHING 2 INCHES. A HIGH
RISK OF HEAVY PRECIPITATION WAS CONSIDERED FOR THE OUTLOOK BASED ON THE ECMWF
PET DEPICTING CHANCES IN EXCESS OF 60% OVER CALIFORNIA, THOUGH THIS IS LESS
SUPPORTED BY THE GEFS PET AND OVERALL LACK OF SIGNALS IN THE IVT TOOLS. BASED
ON THESE WETTER TRENDS AND SUPPORT FROM THE SNOW WATER EQUIVALENT (SWE) PET, A
SLIGHT AND MODERATE RISK OF HIGH ELEVATION SNOW ARE POSTED OVER THE KLAMATH AND
SIERRA NEVADA RANGES OF CALIFORNIA (FEB 16-21 AND FEB 17-21, RESPECTIVELY) AS
WELL AS OVER PARTS OF THE DESERT SOUTHWEST, ROCKIES, AND GREAT BASIN (FEB 17-21
AND FEB 17-20, RESPECTIVELY). A SLIGHT RISK OF HIGH WINDS IS ALSO POSTED FOR
FEB 16-21 OVER MUCH OF THE WEST COAST GIVEN THE FAVORED AMPLIFICATION OF THE
TROUGHING ALOFT SIGNALS IN THE PETS. DESPITE THE FAVORED RETURN OF ABOVE-NORMAL
AND POTENTIALLY HEAVY PRECIPITATION FOLLOWING AN AR ACTIVITY THAT HAS ADVERSELY
IMPACTED THE WEST, NO FLOODING POSSIBLE HAZARDS ARE DESIGNATED AT THIS TIME DUE
TO THE LENGTH OF DRYING OUT DURING MUCH OF WEEK-1 AND INTO EARLY WEEK-2. A
PERIOD OF BELOW-NORMAL PRECIPITATION SHOULD ALLOW REGIONAL STREAMS AND RIVER
LEVELS TO SUBSIDE, HOWEVER, LOCALIZED FLOODING REMAINS POSSIBLE, ESPECIALLY IF
THE FAVORED STORMINESS PRODUCES HIGH PRECIPITATION RATES DURING THE WEEK-2
PERIOD, WHICH MAY BE EXACERBATED BY SNOWPACK BUILDUP AT LOWER ELEVATIONS IN
RECENT WEEKS.
EARLY IN THE PERIOD, ENSEMBLES SUGGEST THE POTENTIAL FOR SHORTWAVE ENERGY
PROPAGATING EASTWARD OVER THE LOWER LATITUDES OVER NORTH AMERICA WITH INCREASED
PRECIPITATION AMOUNTS FAVORED OVER MEXICO AND THE GULF STATES. THE WEATHER
PREDICTION CENTER (WPC) DAY 7 FORECAST CONTINUES TO FEATURE A QUASI-STATIONARY
FRONTAL BOUNDARY DRAPED OVER THE SOUTHERN TIER OF THE CONUS WHICH, AT LEAST
INITIALLY, LOOKS TO SERVE AS THE MAIN SURFACE FORCING FEATURE, AND BOTH RAW AND
CALIBRATED PRECIPITATION TOOLS HAVE BEEN CONSISTENT INDICATING INCREASED
CHANCES FOR HEAVY PRECIPITATION EARLY IN WEEK-2. BY DAYS 10-11, BOTH THE GEFS
AND ECMWF ENSEMBLES SHOW INDICATIONS OF SURFACE LOW DEVELOPMENT OVER THE GULF
OF MEXICO TO REINFORCE THE HEAVY PRECIPITATION THREAT OVER THE EASTERN AND
CENTRAL GULF STATES THROUGH THE MIDDLE OF THE PERIOD. AS THE MEAN SURFACE LOW
TRACKS INTO THE ATLANTIC, THE INFLUX OF LOW-LEVEL MOISTURE INCREASES THE
POTENTIAL FOR HEAVY PRECIPITATION OVER THE SOUTHEAST AND LOWER MID-ATLANTIC
WHICH IS REFLECTED IN THE PETS IN THE BACKEND OF THE PERIOD. TO CAPTURE THE
SYNOPTIC EVOLUTION, A PAIR OF SLIGHT RISKS OF HEAVY PRECIPITATION ARE POSTED,
ONE FOCUSED OVER SOUTHEASTERN TEXAS AND LOUISIANA FOR FEB 15-17, AND THE OTHER
EXTENDING FROM THE LOWER MISSISSIPPI VALLEY EASTWARD TO THE LOWER EASTERN
SEABOARD FOR FEB 17-20. WITH ANOMALOUSLY COLD TEMPERATURES FAVORED TO BE IN
PLACE, HIGH ELEVATION HEAVY SNOW IS POSSIBLE LATER IN THE PERIOD OVER THE
SOUTHERN APPALACHIANS WHICH IS MARGINALLY SUPPORTED BY THE GEFS SWE TOOL. NO
CORRESPONDING HAZARDS ARE ISSUED AT THIS TIME DUE TO UNCERTAINTY AT THIS LEAD,
BUT ANY SNOW POTENTIAL OVER THE EASTERN CONUS WILL BE MONITORED IN UPCOMING
OUTLOOKS.
THERE CONTINUES TO BE PERSISTENT 500-HPA TROUGHING AND SURFACE LOW PRESSURE
FORECAST OVER THE CANADIAN MARITIMES TO HELP USHER IN COLDER TEMPERATURES
THROUGHOUT MUCH OF THE EASTERN CONUS. WHILE MINIMUM TEMPERATURES ARE NOT
EXPECTED TO REACH HAZARD THRESHOLDS ASSOCIATED WITH THE ANOMALOUSLY COLD AIR
MASS (THOUGH SOME LOCATIONS IN THE SOUTHEAST MAY EXPERIENCE MINIMUM
TEMPERATURES DIPPING BELOW FREEZING TOWARDS THE MIDDLE OF THE PERIOD),
STRENGTHENING HIGH SURFACE PRESSURE FAVORED TO THE WEST OF THE OFFSHORE LOW MAY
INDUCE PERIODS OF HIGH WINDS OVER THE NORTHEASTERN CONUS. THEREFORE, A SLIGHT
RISK OF HIGH WINDS REMAINS ISSUED OVER PARTS OF THE GREAT LAKES, OHIO VALLEY,
APPALACHIANS, MID-ATLANTIC AND NORTHEAST FOR FEB 15-19.
OVER EASTERN TEXAS, THERE IS CURRENTLY MINOR STREAM AND RIVER FLOODING IN
PROGRESS. UP TO AN INCH OF RAIN IS FORECAST ACROSS THIS REGION DURING THE
WEEK-1 PERIOD, WITH ADDITIONAL PRECIPITATION EXPECTED DURING WEEK-2. THOUGH NO
FLOOD RISK IS POSTED FOR EASTERN TEXAS AT THIS TIME, THIS POTENTIAL STILL
WARRANTS MONITORING.
OVER ALASKA, MUCH OF THE ENHANCED ONSHORE FLOW OVER THE ALEUTIANS AND ALASKA
COAST LOOKS TO TIME OFF BY THE START OF WEEK-2 WITH MID-LEVEL ANOMALOUS RIDGING
FAVORED TO OVERSPREAD MUCH OF THE STATE. AS A RESULT, THE SLIGHT RISK OF HEAVY
PRECIPITATION IS DISCONTINUED FROM THE OUTLOOK. STRONG SURFACE HIGH PRESSURE
ESTABLISHED OVER THE YUKON TERRITORY MAY INDUCE GAP WINDS ACROSS THE SOUTHEAST
BUT THIS HAZARD POTENTIAL IS NOT SUPPORTED BY THE PETS.
FORECASTER: NICK NOVELLA
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